1. Field of the Invention
The present invention relates to a retrievable drug delivery stent which is made of a hollow tubular wire and which can be carried on a balloon of a balloon catheter to a site of a stenotic lesion where the stent is implanted. Subsequently, a balloon catheter can be inserted into the area of the stenotic lesion and a balloon can be positioned within the stent and by heating or cooling the stent with fluid supplied to the balloon, causing the stent to take another form, namely a retracted form. Then the stent and balloon can be removed. The hollow tubular wire stent is preferably made of a metal, such as stainless steel, tantalum or perhaps even from a nickel titanium alloy sold under the trademark Nitinol which can assume different shapes based upon the temperature of the Nitinol.TM.. The tubing has holes therein for delivering a liquid solution or drug to a stenotic lesion. The hollow tubular wire stent also can be made of a plastic material.
2. Description of the related art including information disclosed under 37 C.F.R. 21211.97-1.99
Heretofore, wire stents have been proposed and one example of an undulating wire stent which extends in an undulating pattern back and forth in circular paths connected by loops to form a generally cylindrical envelope and which is adapted to be received on a balloon of a balloon catheter for insertion into a blood vessel to a site of a stenotic lesion is disclosed in the Gianturco U.S. Pat. No. 5,041,126.
Another example of a wire stent, preferably made of Nitinol.TM. that extends in an undulating manner in a helical path in a cylindrical envelope is disclosed in the Pinchuk U.S. Pat. No. 5,019,090.
A stent delivery system, which includes a sheath that is received about a balloon carrying a stent for facilitating insertion of the assembly of the sheath, stent, and balloon on a wire guidewire to a site of a stenotic lesion is disclosed in the Lau et al. U.S. Pat. No. 5,158,548.
Further, there has been disclosed in the Silverstrini U.S. Pat. No. 5,234,456, a hydrophilic stent which can be made of hollow tubular members. The hollow walls of the tubular members have hydrophilic material therein containing a drug and are fabricated of a semi-permeable material so that liquid can pass therethrough to swell the hydrophilic material.
As will be described in greater detail hereinafter, the hollow tubular stent of the present invention extends in a cylindrical envelope about a balloon and has holes therein that face outwardly of the cylindrical envelope whereby a drug can be delivered to the area of a stenotic lesion through the holes in the hollow wire tubular stent. After the stent is implanted at the site of the stenotic lesion and a fluid delivery tube is left in place connected to the stent for supplying liquid thereto, such as a liquid containing a drug, after a short period of time (a few days to a week or more), a dissolving fluid can be inserted into the liquid delivery tube for dissolving an end portion of the tube to disconnect the tube from the stent. Then, a balloon on a balloon catheter or a balloon on a wire guidewire can be reinserted into the vessel to the area of the stenotic lesion and partially inflated to assist in the withdrawal of the tubular wire stent from the area of the stenotic lesion.
The drug delivered to the area of the stenotic lesion can be of the type which dissolves plaque material forming the stenosis or can be an anti-platelet formation drug or an anti-thrombotic drug. Such drugs can include TPA, heparin, or urokinase, for example.